package io.polaris.core.codec;

import java.io.IOException;
import java.io.OutputStream;

/**
 * @author Qt
 * @since 1.8
 */
public class Base32Encoder implements Encoder {
	private static final byte[] DEFAULT_ENCODING_TABLE =
		{
			(byte) 'A', (byte) 'B', (byte) 'C', (byte) 'D', (byte) 'E', (byte) 'F', (byte) 'G',
			(byte) 'H', (byte) 'I', (byte) 'J', (byte) 'K', (byte) 'L', (byte) 'M', (byte) 'N',
			(byte) 'O', (byte) 'P', (byte) 'Q', (byte) 'R', (byte) 'S', (byte) 'T', (byte) 'U',
			(byte) 'V', (byte) 'W', (byte) 'X', (byte) 'Y', (byte) 'Z',
			(byte) '2', (byte) '3', (byte) '4', (byte) '5', (byte) '6', (byte) '7'
		};

	private static final byte DEFAULT_PADDING = (byte) '=';

	/*
	 * set up the decoding table.
	 */
	private final byte[] encodingTable;
	private final byte padding;
	private final byte[] decodingTable = new byte[128];


	/**
	 * Base constructor for RFC 4648, Section 6.
	 */
	public Base32Encoder() {
		this.encodingTable = DEFAULT_ENCODING_TABLE;
		this.padding = DEFAULT_PADDING;

		initialiseDecodingTable();
	}

	/**
	 * Constructor allowing the setting of an alternative alphabet.
	 *
	 * @param encodingTable a 32 entry encoding table to do the mapping.
	 * @param padding       the padding value to use.
	 */
	public Base32Encoder(byte[] encodingTable, byte padding) {
		if (encodingTable.length != 32) {
			throw new IllegalArgumentException("encoding table needs to be length 32");
		}

		this.encodingTable = encodingTable.clone();
		this.padding = padding;

		initialiseDecodingTable();
	}

	protected void initialiseDecodingTable() {
		for (int i = 0; i < decodingTable.length; i++) {
			decodingTable[i] = (byte) 0xff;
		}

		for (int i = 0; i < encodingTable.length; i++) {
			decodingTable[encodingTable[i]] = (byte) i;
		}
	}

	public int encode(byte[] inBuf, int inOff, int inLen, byte[] outBuf, int outOff) throws IOException {
		int inPos = inOff;
		int inEnd = inOff + inLen - 4;
		int outPos = outOff;

		while (inPos < inEnd) {
			encodeBlock(inBuf, inPos, outBuf, outPos);
			inPos += 5;
			outPos += 8;
		}

		int extra = inLen - (inPos - inOff);
		if (extra > 0) {
			byte[] in = new byte[5];
			System.arraycopy(inBuf, inPos, in, 0, extra);
			encodeBlock(in, 0, outBuf, outPos);
			switch (extra) {
				case 1:
					outBuf[outPos + 2] = padding;
					outBuf[outPos + 3] = padding;
					outBuf[outPos + 4] = padding;
					outBuf[outPos + 5] = padding;
					outBuf[outPos + 6] = padding;
					outBuf[outPos + 7] = padding;
					break;
				case 2:
					outBuf[outPos + 4] = padding;
					outBuf[outPos + 5] = padding;
					outBuf[outPos + 6] = padding;
					outBuf[outPos + 7] = padding;
					break;
				case 3:
					outBuf[outPos + 5] = padding;
					outBuf[outPos + 6] = padding;
					outBuf[outPos + 7] = padding;
					break;
				case 4:
					outBuf[outPos + 7] = padding;
					break;
			}

			outPos += 8;
		}

		return outPos - outOff;
	}

	private void encodeBlock(byte[] inBuf, int inPos, byte[] outBuf, int outPos) {
		int a1 = inBuf[inPos++];
		int a2 = inBuf[inPos++] & 0xFF;
		int a3 = inBuf[inPos++] & 0xFF;
		int a4 = inBuf[inPos++] & 0xFF;
		int a5 = inBuf[inPos] & 0xFF;

		outBuf[outPos++] = encodingTable[(a1 >>> 3) & 0x1F];
		outBuf[outPos++] = encodingTable[((a1 << 2) | (a2 >>> 6)) & 0x1F];
		outBuf[outPos++] = encodingTable[(a2 >>> 1) & 0x1F];
		outBuf[outPos++] = encodingTable[((a2 << 4) | (a3 >>> 4)) & 0x1F];
		outBuf[outPos++] = encodingTable[((a3 << 1) | (a4 >>> 7)) & 0x1F];
		outBuf[outPos++] = encodingTable[(a4 >>> 2) & 0x1F];
		outBuf[outPos++] = encodingTable[((a4 << 3) | (a5 >>> 5)) & 0x1F];
		outBuf[outPos] = encodingTable[a5 & 0x1F];
	}

	@Override
	public int getEncodedLength(int inputLength) {
		return (inputLength + 4) / 5 * 8;
	}

	@Override
	public int getMaxDecodedLength(int inputLength) {
		return inputLength / 8 * 5;
	}

	/**
	 * encode the input data producing a base 32 output stream.
	 *
	 * @return the number of bytes produced.
	 */
	@Override
	public int encode(byte[] buf, int off, int len, OutputStream out)
		throws IOException {
		if (len < 0) {
			return 0;
		}

		byte[] tmp = new byte[72];
		int remaining = len;
		while (remaining > 0) {
			int inLen = Math.min(45, remaining);
			int outLen = encode(buf, off, inLen, tmp, 0);
			out.write(tmp, 0, outLen);
			off += inLen;
			remaining -= inLen;
		}
		return (len + 2) / 3 * 4;
	}

	private boolean ignore(
		char c) {
		return (c == '\n' || c == '\r' || c == '\t' || c == ' ');
	}

	/**
	 * decode the base 32 encoded byte data writing it to the given output stream,
	 * whitespace characters will be ignored.
	 *
	 * @return the number of bytes produced.
	 */
	@Override
	public int decode(
		byte[] data,
		int off,
		int length,
		OutputStream out)
		throws IOException {
		byte b1, b2, b3, b4, b5, b6, b7, b8;
		byte[] outBuffer = new byte[55];
		int bufOff = 0;
		int outLen = 0;

		int end = off + length;

		while (end > off) {
			if (!ignore((char) data[end - 1])) {
				break;
			}

			end--;
		}

		// empty data!
		if (end == 0) {
			return 0;
		}

		int i = 0;
		int finish = end;

		while (finish > off && i != 8) {
			if (!ignore((char) data[finish - 1])) {
				i++;
			}

			finish--;
		}

		i = nextI(data, off, finish);

		while (i < finish) {
			b1 = decodingTable[data[i++]];

			i = nextI(data, i, finish);

			b2 = decodingTable[data[i++]];

			i = nextI(data, i, finish);

			b3 = decodingTable[data[i++]];

			i = nextI(data, i, finish);

			b4 = decodingTable[data[i++]];

			i = nextI(data, i, finish);

			b5 = decodingTable[data[i++]];

			i = nextI(data, i, finish);

			b6 = decodingTable[data[i++]];

			i = nextI(data, i, finish);

			b7 = decodingTable[data[i++]];

			i = nextI(data, i, finish);

			b8 = decodingTable[data[i++]];

			if ((b1 | b2 | b3 | b4 | b5 | b6 | b7 | b8) < 0) {
				throw new IOException("invalid characters encountered in base32 data");
			}

			outBuffer[bufOff++] = (byte) ((b1 << 3) | (b2 >> 2));
			outBuffer[bufOff++] = (byte) ((b2 << 6) | (b3 << 1) | (b4 >> 4));
			outBuffer[bufOff++] = (byte) ((b4 << 4) | (b5 >> 1));
			outBuffer[bufOff++] = (byte) ((b5 << 7) | (b6 << 2) | (b7 >> 3));
			outBuffer[bufOff++] = (byte) ((b7 << 5) | b8);

			if (bufOff == outBuffer.length) {
				out.write(outBuffer);
				bufOff = 0;
			}

			outLen += 5;

			i = nextI(data, i, finish);
		}

		if (bufOff > 0) {
			out.write(outBuffer, 0, bufOff);
		}

		int e0 = nextI(data, i, end);
		int e1 = nextI(data, e0 + 1, end);
		int e2 = nextI(data, e1 + 1, end);
		int e3 = nextI(data, e2 + 1, end);
		int e4 = nextI(data, e3 + 1, end);
		int e5 = nextI(data, e4 + 1, end);
		int e6 = nextI(data, e5 + 1, end);
		int e7 = nextI(data, e6 + 1, end);

		outLen += decodeLastBlock(out,
			(char) data[e0], (char) data[e1], (char) data[e2], (char) data[e3],
			(char) data[e4], (char) data[e5], (char) data[e6], (char) data[e7]);

		return outLen;
	}

	private int nextI(byte[] data, int i, int finish) {
		while ((i < finish) && ignore((char) data[i])) {
			i++;
		}
		return i;
	}

	/**
	 * decode the base 32 encoded String data writing it to the given output stream,
	 * whitespace characters will be ignored.
	 *
	 * @return the number of bytes produced.
	 */
	@Override
	public int decode(String data, OutputStream out) throws IOException {
		byte[] bytes = CodecStrings.toByteArray(data);
		return decode(bytes, 0, bytes.length, out);
	}


	private int decodeLastBlock(OutputStream out,
		char c1, char c2, char c3, char c4,
		char c5, char c6, char c7, char c8)
		throws IOException {
		byte b1, b2, b3, b4, b5, b6, b7, b8;

		if (c8 == padding) {
			if (c7 != padding) {
				b1 = decodingTable[c1];
				b2 = decodingTable[c2];
				b3 = decodingTable[c3];
				b4 = decodingTable[c4];
				b5 = decodingTable[c5];
				b6 = decodingTable[c6];
				b7 = decodingTable[c7];

				if ((b1 | b2 | b3 | b4 | b5 | b6 | b7) < 0) {
					throw new IOException("invalid characters encountered at end of base32 data");
				}

				out.write((b1 << 3) | (b2 >> 2));
				out.write((b2 << 6) | (b3 << 1) | (b4 >> 4));
				out.write((b4 << 4) | (b5 >> 1));
				out.write((b5 << 7) | (b6 << 2) | (b7 >> 3));

				return 4;
			}
			if (c6 != padding) {
				throw new IOException("invalid characters encountered at end of base32 data");
			}

			if (c5 != padding) {
				b1 = decodingTable[c1];
				b2 = decodingTable[c2];
				b3 = decodingTable[c3];
				b4 = decodingTable[c4];
				b5 = decodingTable[c5];

				if ((b1 | b2 | b3 | b4 | b5) < 0) {
					throw new IOException("invalid characters encountered at end of base32 data");
				}

				out.write((b1 << 3) | (b2 >> 2));
				out.write((b2 << 6) | (b3 << 1) | (b4 >> 4));
				out.write((b4 << 4) | (b5 >> 1));

				return 3;
			}

			if (c4 != padding) {
				b1 = decodingTable[c1];
				b2 = decodingTable[c2];
				b3 = decodingTable[c3];
				b4 = decodingTable[c4];

				if ((b1 | b2 | b3 | b4) < 0) {
					throw new IOException("invalid characters encountered at end of base32 data");
				}

				out.write((b1 << 3) | (b2 >> 2));
				out.write((b2 << 6) | (b3 << 1) | (b4 >> 4));

				return 2;
			}

			if (c3 != padding) {
				throw new IOException("invalid characters encountered at end of base32 data");
			}

			b1 = decodingTable[c1];
			b2 = decodingTable[c2];

			if ((b1 | b2) < 0) {
				throw new IOException("invalid characters encountered at end of base32 data");
			}

			out.write((b1 << 3) | (b2 >> 2));

			return 1;
		} else {
			b1 = decodingTable[c1];
			b2 = decodingTable[c2];
			b3 = decodingTable[c3];
			b4 = decodingTable[c4];
			b5 = decodingTable[c5];
			b6 = decodingTable[c6];
			b7 = decodingTable[c7];
			b8 = decodingTable[c8];

			if ((b1 | b2 | b3 | b4 | b5 | b6 | b7 | b8) < 0) {
				throw new IOException("invalid characters encountered at end of base32 data");
			}

			out.write((b1 << 3) | (b2 >> 2));
			out.write((b2 << 6) | (b3 << 1) | (b4 >> 4));
			out.write((b4 << 4) | (b5 >> 1));
			out.write((b5 << 7) | (b6 << 2) | (b7 >> 3));
			out.write((b7 << 5) | b8);

			return 5;
		}
	}
}
